A wound is generally defined as a break in the epithelial integrity of the skin. Such an injury, however, may be much deeper, including the dermis, subcutaneous tissue, fascia, muscle, and even bone. Proper wound healing is a highly complex, dynamic, and coordinated series of steps leading to tissue repair. Acute wound healing is a dynamic process involving both resident and migratory cell populations acting in a coordinated manner within the extra-cellular matrix environment to repair the injured tissues. Some wounds fail to heal in this manner (for a variety of reasons) and may be referred to as chronic wounds.
Following tissue injury, the coordinated healing of a wound will typically involve four overlapping but well-defined phases: hemostasis, inflammation, proliferation, and remodeling. Hemostasis involves the first steps in wound response and repair which are bleeding, coagulation, and platelet and complement activation. Inflammation peaks near the end of the first day. Cell proliferation occurs over the next 7-30 days and involves the time period over which wound area measurements may be of most benefit. During this time, fibroplasia, angiogenesis, re-epithelialization, and extra-cellular matrix synthesis occur. The initial collagen formation in a wound typically peaks in approximately 7 days. The wound re-epithelialization occurs in about 48 hours under optimal conditions, at which time the wound may be completely sealed. A healing wound may have 15% to 20% of full tensile strength at 3 weeks and 60% of full strength at 4 months. After the first month, a degradation and remodeling stage begins, wherein cellularity and vascularity decrease and tensile strength increases. Formation of a mature scar often requires 6 to 12 months.
There are various wound parameters that may assist a clinician in determining and tracking healing progress of a wound. For example, wound dimensions, including wound area and volume measurements, may provide a clinician with knowledge as to whether or not a wound is healing and, if the wound is healing, how rapidly the wound is healing. Wound assessment is an important process to properly treating a wound, as improper or incomplete assessment may result in a wide variety of complications.
While wound measurements may provide valuable parameters for helping a clinician assess wound healing progress, the size of the wound may not provide a clinician with a full picture to fully assess whether or how a wound is healing. For example, while the size of a wound may be reduced during treatment, certain parts of a wound may become infected. A clinician may often-times examine wound tissue for its color and texture to determine how a wound is healing. Wound tissue includes a wound bed and peri-wound areas or wound edges. Health of a wound may be determined by color of tissue, with certain problems often presenting with distinct colors at the wound. For example, normal granulation tissue typically has a red, shiny textured appearance and bleeds readily, whereas necrotic tissue (i.e., dead tissue) may either be yellow-gray and soft, generally known as “slough” tissue, or hard and blackish-brown in color, generally known as “eschar” tissue. A clinician may observe and monitor these and other wound tissues to determine wound healing progress of the overall wound, as well as specific wound regions.
Because wound treatment can be costly in both materials and professional care time, a treatment that is based on an accurate assessment of the wound and the wound healing process can be essential.